Hydroponic systems known in the prior art generally comprise a longitudinally extending trough or coffer having an upward opening, and a pumping system for circulating a nutrient solution through the container. It is also common to employ a growing medium such as sawdust, sand, gravel, exfoliated mineral products, rock wool cubes, or other media that provide structural support for the plant roots and easy circulation of the solution.
The upward opening of most hydroponic systems permits a large amount of evaporation from the system, causing a great deal of water loss. In a greenhouse setting, this has the effect of raising the humidity significantly and requiring the use of dehumidifiers and adding substantially to energy costs. In an outdoor setting the water loss must be compensated, requiring constant water level checking, and testing for nutrient concentration and pH level. Moreover, this waste of large amounts of water negates a major feature of hydroponics; i.e., its inherent conservation of materials and control of growing conditions.
The exposure of the container and its contents to light and sunlight also promotes the growth of algae and the like in the nutrient-rich media. This unwanted growth is parasitic in the system, in that is consumes nutrients intended for productive plant growth. Furthermore, the algae can clog the pumps and filters, causing increased maintenance costs and labor.
The growing media itself also fosters the growth of unwanted and damaging microorganisms, due to the non-sterile nature of the media and the fertile growing conditions. Such microorganisms can attack the plants directly, or can cause indirect damage through toxin release, pH changes in the media, and the like. The use of algicides, fungicides, and anti-bacterial agents adds a great expense to hydroponic operations, and also affect the quality and production of the plants. Also, a growing media that becomes contaminated with destructive agents can be very difficult to clean and restore to productive use.